Water is a covalent compound formed by oxygen and hydrogen. These two elements, due to the differences in their atomic configurations, have different electronegativites. Electronegativity is the relative attraction of electrons to an atom. Oxygen is much more electronegative than hydrogen. Hence the shared electrons are far more likely to be found in the oxygen electron orbitals than the hydrogen electron orbitals. This causes formation of two charge centers in the water molecule. The region near the oxygen atom will have slightly negative charge, while the region near hydrogen atom will have slightly positive charge. This charge separation makes the water molecule polar. This is the very reason for calling water a universal solvent. Because of its polar nature, water is capable of dissolving a large number of compounds, such as common salt, minerals, blood, etc.
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